If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Can DragonFly's HAMMER Compete With Btrfs, ZFS?

01-07-2011, 02:00 AM

Phoronix: Can DragonFly's HAMMER Compete With Btrfs, ZFS?

The most common Linux file-systems we talk about at Phoronix are of course Btrfs and EXT4 while the ZFS file-system, which is available on Linux as a FUSE (user-space) module or via a recent kernel module port, gets mentioned a fair amount too. When it comes to the FreeBSD and PC-BSD operating systems, ZFS is looked upon as the superior, next-generation option that is available to BSD users. However, with the DragonFlyBSD operating system there is another option: HAMMER. In this article we are seeing how the performance of this original creation within the DragonFlyBSD project competes with ZFS, UFS, EXT3, EXT4, and Btrfs.

Comment

There is something seriously wrong with the Threaded I/O tester results. There is simply no way possible that the ZFS writes got faster when switching from linear to random writes, especially considering that all but HAMMER and btrfs went down by an order of magnitude. Are you sure the result wasn't supposed to be 4.96?

I feel that this makes all of your results quite suspect.

Comment

Also, the blogbench results indicate that you ran the benchmark and seperated the read and write results to create the independent graphs. You should point this out in your article. For heavy concurrent read/write workloads where read performance is important DragonFly would recommend the use of the fairq disk scheduler.

Comment

There is something seriously wrong with the Threaded I/O tester results. There is simply no way possible that the ZFS writes got faster when switching from linear to random writes, especially considering that all but HAMMER and btrfs went down by an order of magnitude. Are you sure the result wasn't supposed to be 4.96?

I feel that this makes all of your results quite suspect.

It is of course possible. You just need to know who ZFS works. And know for what kind of workloads it was designed for.

Comment

It is quite easy to explain (log structured writes, more scalable techniques, and probably some bugs in btrfs), but I just do not have time

PS. Stupid 1 minute limit.

Fortunately, I am familiar with the internals of UFS, ZFS and HAMMER. HAMMER is "log structured" in the same fashion as ZFS. Being log structured does nothing to explain the -increase- in performance seen between the final two graphs. These benchmarks are absolutely useless unless the inconsistencies can be explained.

Comment

Hmm, @thesjg you are right. Last graph alone (random write) could be valid, but comparing it to the previous (continious write) indeed bring some questions. Maybe data was not written to disk and combined in cache before doing sync. One should use LOT bigger files than avalable RAM (but unfortunetly random write will take lots of time), and good random generator. Needs more investigation.